ABSTRACT
Background Heterogeneity of the population in relation to infection, COVID-19 vaccination and host characteristics is likely reflected in the underlying SARS-CoV-2 antibody responses.Methods We measured IgM, IgA and IgG levels against SARS-CoV-2 spike and nucleocapsid antigens in 1,076 adults of a cohort study in Catalonia between June-November 2020 and a second time between May-July 2021. Questionnaire data and electronic health records on vaccination and COVID-19 testing were available in both periods.Results Antibody seroreversion occurred in 35.8% of the 64 participants infected almost a year ago and non-vaccinated, and was related to asymptomatic infection, age above 60 years and smoking. Among vaccinated, 2.1% did not present antibodies at the time of testing. In previously infected individuals, vaccination boosted the immune response and there was a slight but statistically significant increase in responses after a 2nd compared to 1st dose. Infected vaccinated participants had superior antibody levels across time compared to naïve vaccinated people. mRNA vaccines and, particularly the Spikevax, induced higher antibodies after 1st and 2nd doses compared to Vaxzevria or Janssen COVID-19 vaccines. In multivariable regression analyses, antibody responses after vaccination were predicted by type of vaccine, infection age, sex, smoking, mental and cardiovascular diseases.Conclusions Our data support that infected people would benefit from vaccination. Results also indicate that hybrid immunity results in superior antibody responses and infection-naïve people would need a booster dose earlier than previously infected people. Mental diseases are associated with less efficient response to vaccination.
Subject(s)
COVID-19ABSTRACT
Unraveling long-term kinetics of antibodies to SARS-CoV-2 and the factors influencing its course, like prior antibody levels to human coronaviruses causing common cold (HCoVs), is essential to understand protective immunity and effective surveillance strategies. Antibody levels against six SARS-CoV-2 and four HCoV antigens were quantified by Luminex, and antibody neutralization capacity was assessed by flow cytometry in a cohort of health care workers followed-up for 6 months. Seroprevalence increased over time from 13.5% (month 0) and 15.6% (month 1), to 16.4% (month 6). Levels of antibodies were stable over time, except IgG against nucleocapsid antigen and IgM levels that waned. After the peak response, anti-spike antibody levels increased from ~150 days post-symptom onset in all individuals (73% for IgG), in the absence of any evidence of re-exposure. The neutralizing capacity of antibodies was maintained. Pre-existing antibodies to alpha-HCoV were lower in individuals who subsequently seroconverted for SARS-CoV-2. IgG and IgA to HCoV were significantly higher in asymptomatic than symptomatic seropositive individuals. Thus, pre-existing cross-reactive HCoVs antibodies could have a protective effect against SARS-CoV-2 infection and COVID-19 disease.
Subject(s)
COVID-19ABSTRACT
We assessed the duration and baseline determinants of antibody responses to SARS-CoV-2 spike antigens and the occurrence of reinfections in a prospective cohort of 173 Spanish primary health care worker patients followed up initially for nine months and subsequently up to 12.5 months after COVID-19 symptoms onset. Seropositivity to SARS-CoV-2 spike and receptor binding domain antigens up to 149-270 days was 92.49% (90.17% IgG, 76.3% IgA, 60.69% IgM). In a subset of 64 health care workers who had not yet been vaccinated by April 2021, seropositivity was 96.88% (95.31% IgG, 82.81% IgA) up to 322-379 days post symptoms onset. There were four suspected reinfections detected by passive case detection, two among seronegative individuals (five and seven months after the first episode), and one low antibody responder. Antibody levels significantly correlated with fever, hospitalization, anosmia/hypogeusia, allergies, smoking and occupation. Stable sustainment of IgG responses raises hope for long-lasting COVID-19 vaccine immunity.
Subject(s)
COVID-19ABSTRACT
Reliable serological tests are required to determine the prevalence of antibodies against SARS-CoV-2 antigens and to characterise immunity to the disease in order to address key knowledge gaps in the context of the COVID-19 pandemic. Quantitative suspension array technology (qSAT) assays based on the xMAP Luminex platform overcome the limitations of rapid diagnostic tests and ELISA with their higher precision, dynamic range, throughput, miniaturization, cost-efficacy and multiplexing capacity. We developed three qSAT assays to detect IgM, IgA and IgG to a panel of eight SARS-CoV-2 antigens including spike (S), nucleoprotein (N) and membrane (M) protein constructs. The assays were optimized to minimize processing time and maximize signal to noise ratio. We evaluated the performance of the assays using 128 plasmas obtained before the COVID-19 pandemic (negative controls) and 115 plasmas from individuals with SARS-CoV-2 diagnosis (positive controls), of whom 8 were asymptomatic, 58 had mild symptoms and 49 were hospitalized. Pre-existing IgG antibodies recognizing N, M and S2 proteins were detected in negative controls suggestive of cross-reactive to common cold coronaviruses. The best performing antibody isotype/antigen signatures had specificities of 100% and sensitivities of 94.94% at [≥]14 days since the onset of symptoms and 96.08% at [≥]21 days since the onset of symptoms, with AUC of 0.992 and 0.999, respectively. Combining multiple antibody markers as assessed by qSAT assays has the highest efficiency, breadth and versatility to accurately detect low-level antibody responses for obtaining reliable data on prevalence of exposure to novel pathogens in a population. Our assays will allow gaining insights into antibody correlates of immunity required for vaccine development to combat pandemics like the COVID-19.